阅读说明：本技术 一种流动性好的高熔点覆膜砂 (High-melting-point precoated sand with good fluidity ) 是由 余俊 潘是凯 于 2021-09-29 设计创作，主要内容包括：本发明公开了一种流动性好的高熔点覆膜砂,属于覆膜砂制造技术领域。本发明首先在石英砂中按一定比例掺杂碳纳米管、纳米氧化钇与铬矿砂混合制得一种混制骨料,所得混制骨料耐火度高、挥发物少、强度高,且制备方法简单、价格较低。将该混制骨料与粘结剂、固化剂、润滑剂加热混砂,制得一种流动性好的高熔点覆膜砂,本发明有效解决了常规覆膜砂粘砂、变形、热裂、气孔等铸造缺陷,制备方法简单,具有良好的应用前景。(The invention discloses high-melting-point precoated sand with good fluidity, and belongs to the technical field of precoated sand manufacturing. According to the invention, firstly, the quartz sand is doped with the carbon nano tube, the nano yttrium oxide and the chromium ore sand according to a certain proportion to prepare the mixed aggregate, and the obtained mixed aggregate has high refractoriness, less volatile matter, high strength, simple preparation method and lower price. The invention effectively solves the casting defects of sand sticking, deformation, heat cracking, air holes and the like of the conventional precoated sand, and has simple preparation method and good application prospect.)

1. The high-melting-point precoated sand with good fluidity is characterized by comprising the following raw materials in parts by weight:

200 parts of mixed aggregate is prepared, and the mixture is stirred,

6-11 parts of thermoplastic phenolic resin,

0.3 to 0.55 portion of coupling agent,

0.5 to 0.8 portion of urotropin,

0.8-0.9 part of lubricant;

the raw materials for preparing the mixed aggregate comprise quartz sand, chromium ore sand, carbon nano tubes and yttrium oxide;

the chromium ore sand accounts for 12-17% of the mass of the quartz sand, the carbon nano tube accounts for 1.4-3.0% of the mass of the quartz sand, and the yttrium oxide accounts for 6.5-8.4% of the mass of the quartz sand.

2. The high-melting-point precoated sand with good fluidity according to claim 1, wherein Cr in the chromium ore sand is Cr₂O₃Not less than 48% of Fe₂O₃The content is not higher than 19%.

3. The high-melting-point precoated sand with good fluidity according to claim 1, wherein the carbon nanotubes are pretreated before being mixed: according to the mass volume ratio (g/mL) of 1: 20 mixing the carbon nano tube with an acid solution, heating to 70-110 ℃, performing ultrasonic and magnetic stirring, performing condensation reflux for 3 hours, washing, filtering and drying.

4. The high-melting-point precoated sand with good fluidity according to claim 3, wherein the acid solution is prepared by mixing 75 mass percent of sulfuric acid and 60 mass percent of nitric acid in a volume ratio of 1: 1.6 to 1.8.

5. The high-melting-point precoated sand with good fluidity according to claim 1, wherein the preparation method of the mixed aggregate comprises the following steps: weighing each raw material of the mixed aggregate according to the proportion, taking the chrome sand and the carbon nano tube, mixing and stirring for 10min at the rotating speed of 800-1200r/min, then adding the obtained mixture into the quartz sand calcined at 900 ℃ for 2h, mixing and stirring for 50min at the rotating speed of 1500-2500r/min, then adding the yttrium oxide, and continuing stirring for 20 min.

6. The high-melting-point precoated sand with good fluidity according to claim 5, wherein the yttrium oxide is nano yttrium oxide, the purity of the yttrium oxide is not less than 99.99%, and the particle size is 30-50 nm.

7. The high-melting-point precoated sand with good fluidity according to claim 1, wherein the urotropine is a hexamethylenetetramine aqueous solution with a mass fraction of 40%.

8. A method for preparing high-melting-point precoated sand with good fluidity according to any one of claims 1 to 7, which is characterized by comprising the following steps:

A. weighing the raw materials according to the proportion for later use;

B. heating the mixed aggregate to 135-160 ℃, transferring the mixed aggregate into a sand mixer, and adding the thermoplastic phenolic resin and the coupling agent for sand mixing for 60-80 s;

C. c, when the temperature of the mixture in the step B is cooled to 90-110 ℃, adding urotropine sand mixing for 30-40 s;

D. and C, cooling the mixture in the step C to 80 ℃, adding a lubricant for mixing sand for 30s, immediately discharging the sand, crushing and screening to obtain the precoated sand.

9. The method for preparing high-melting-point precoated sand with good fluidity according to claim 8, wherein the coupling agent in the step B is prepared from KH550 and KH560 according to an equal mass ratio.

10. The method for preparing high-melting-point precoated sand with good fluidity according to claim 8, wherein the addition amount of the coupling agent in the step B is 0.5% of that of the thermoplastic phenolic resin.

Technical Field

The invention belongs to the technical field of precoated sand manufacturing, and particularly relates to high-melting-point precoated sand with good fluidity.

Background

The precoated sand molding method was invented by J.Croning in Germany in 1944, and introduced and popularized in 1953 in Japan. In the initial stage of the invention, powdered phenolic resin and a hardening agent are mixed into silica sand to form the phenolic resin-silica sand; then, the precoated sand is prepared by thermoplastic phenolic resin, latent curing agent (hexamethylenetetramine) and lubricant through a certain coating process, when the precoated sand is heated, the resin coated on the surface of sand grains is melted, and the melted resin is quickly converted from a linear structure into a non-melted body structure under the action of methylene decomposed from the hexamethylenetetramine, so that the precoated sand is cured and molded.

However, in the existing precoated sand preparation process, because phenolic resin is generally adopted as a binder, although the phenolic resin has good binding property, the phenolic resin has high viscosity, which causes poor flowability of the precoated sand, thereby affecting the processability and precision of subsequent castings; in addition, the phenolic resin has poor heat resistance, which can cause the precoated sand to be easily deformed at high temperature, and causes the defects of sand sticking, heat cracking, air holes and the like; therefore, it is necessary to develop precoated sand having a high melting point and good fluidity.

Disclosure of Invention

Aiming at the problems in the background art, the invention provides high-melting-point precoated sand with good fluidity, which is realized by the following technical scheme:

the high-melting-point precoated sand with good fluidity comprises the following raw materials in parts by weight:

200 parts of mixed aggregate is prepared, and the mixture is stirred,

6-11 parts of thermoplastic phenolic resin,

0.3 to 0.55 portion of coupling agent,

0.5 to 0.8 portion of urotropin,

0.8-0.9 part of lubricant.

Further, the raw materials for preparing the mixed aggregate comprise quartz sand, chrome ore sand, carbon nano tubes and yttrium oxide.

Further, the chromium ore sand accounts for 12% -17% of the mass of the quartz sand, the carbon nano tube accounts for 1.4% -3.0% of the mass of the quartz sand, and the yttrium oxide accounts for 6.5% -8.4% of the mass of the quartz sand.

Further, Cr in the chromium ore sand₂O₃Not less than 48% of Fe₂O₃The content is not higher than 19%.

Furthermore, the AFS granularity of the quartz sand and the chrome sand is 55-65.

The chromium ore sand has better function of resisting alkaline slag, does not react with ferric oxide and the like, and can effectively avoid thermochemical sand adhesion in the actual production and processing; in addition, in the meltIn the molten metal casting process, the chromium ore can be subjected to solid-phase sintering, so that the penetration of molten metal is reduced, and mechanical sand sticking can be prevented. The ratio of chromium and iron elements in the chromium ore is a key factor influencing the performance of the chromium ore, and the invention selects Cr in combination with the preparation process system of the invention₂O₃Not less than 48% of Fe₂O₃The chromium ore with the content not higher than 19 percent is used as a raw material to prepare the aggregate, so that the sand sticking defect of the finally prepared precoated sand is obviously reduced.

Further, the carbon nanotubes need to be pretreated before being mixed: according to the mass volume ratio (g/mL) of 1: 20 mixing the carbon nano tube with an acid solution, heating to 70-110 ℃, performing ultrasonic and magnetic stirring, performing condensation reflux for 3 hours, washing, filtering and drying.

Further, the acid solution is prepared by mixing 75% by mass of sulfuric acid and 60% by mass of nitric acid in a volume ratio of 1: 1.6 to 1.8.

Further, the preparation method of the mixed aggregate comprises the following steps: weighing each raw material of the mixed aggregate according to the proportion, taking the chrome sand and the carbon nano tube, mixing and stirring for 10min at the rotating speed of 800-1200r/min, then adding the obtained mixture into the quartz sand calcined at 900 ℃ for 2h, mixing and stirring for 50min at the rotating speed of 1500-2500r/min, then adding the yttrium oxide, and continuously stirring for 20min to obtain the composite material.

Furthermore, the yttrium oxide is nano yttrium oxide, the purity of the yttrium oxide is not lower than 99.99%, and the particle size is 30-50 nm.

The Carbon Nano Tubes (CNTs) have unique low-dimensional structures and mechanical properties, thermal stability and thermal conductivity, the melting point of the prepared precoated sand can be obviously improved by doping the carbon nano tubes into the aggregate, and the dispersion uniformity of the carbon nano tubes in the thermoplastic phenolic resin can be improved after the carbon nano tubes are subjected to acidification pretreatment; and the nanometer yttrium oxide can effectively reduce the viscosity of the thermoplastic phenolic resin, thereby improving the high-temperature fluidity of the precoated sand. According to the invention, the carbon nano tubes, the nano yttrium oxide and the chromium ore are doped in the quartz sand according to a certain proportion to prepare the mixed aggregate, the aggregate has high refractoriness, few volatile matters and high strength, the preparation method is simple and the price is lower, the precoated sand prepared by using the mixed aggregate has high melting point and good high-temperature fluidity, and the casting defects of sand sticking, deformation, heat cracking, air holes and the like of the conventional precoated sand are effectively overcome.

Further, the urotropin is a hexamethylenetetramine aqueous solution with the mass fraction of 40%.

Further, the lubricant is calcium stearate.

The invention also provides a preparation method of the high-melting-point precoated sand with good fluidity, which comprises the following steps:

A. weighing the raw materials according to the proportion for later use;

B. heating the mixed aggregate to 135-160 ℃, transferring the mixed aggregate into a sand mixer, and adding the thermoplastic phenolic resin and the coupling agent for sand mixing for 60-80 s;

C. c, when the temperature of the mixture in the step B is cooled to 90-110 ℃, adding urotropine sand mixing for 30-40 s;

D. and D, cooling the mixture in the step C to 80 ℃, adding a lubricant for mixing sand for 30s, immediately discharging sand, crushing and screening to obtain the precoated sand.

Further, the coupling agent is prepared from KH550 and KH560 according to an equal mass ratio.

Further, the addition amount of the coupling agent is 0.5% of the thermoplastic phenolic resin.

The invention mixes the KH550 and KH560 with the thermoplastic phenolic resin as the binder, and KH550 is an excellent adhesion promoter, which can improve the adhesion property of the thermoplastic phenolic resin and improve the adhesion with the mixed aggregate; KH560 can improve the compatibility, dispersibility and flowability of the phenolic resin.

Compared with the prior art, the invention has the beneficial effects that:

1. the mixed aggregate for manufacturing the precoated sand is prepared by the invention, the preparation process is simple, the cost is lower, and the mixed aggregate has high refractoriness, few volatile matters and high strength.

2. The precoated sand prepared by the method has high melting point and good high-temperature fluidity, and effectively overcomes the casting defects of sand sticking, deformation, heat cracking, air holes and the like of the conventional precoated sand.

3. The preparation conditions of the precoated sand are similar to those of the conventional precoated sand, the steps are simple, the operation is easy, and the method has a good application prospect.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

1. Weighing 100 parts of quartz sand, 15 parts of chromium ore sand, 2.6 parts of carbon nano tubes and 7.7 parts of nano yttrium oxide according to parts by weight; wherein Cr in the chromium ore sand₂O₃51% of (B), Fe₂O₃The content is 18%, the AFS granularity of quartz sand and chrome sand is 55-65, the nanometer yttrium oxide is not less than 99.99%, the particle size is 30-50nm, the carbon nano tube is pretreated in advance (the carbon nano tube is mixed with acid solution according to the mass volume ratio (g/mL) of 1: 20, the mixture is heated to 100 ℃ for ultrasonic treatment and magnetic stirring, and the mixture is washed, filtered and dried after being condensed and refluxed for 3 hours).

2. Mixing and stirring chrome ore sand and carbon nano tubes for 10min at the rotating speed of 1100r/min, then adding the obtained mixture into quartz sand calcined at 900 ℃ for 2h, mixing and stirring at the rotating speed of 2400r/min for 50min, adding nano yttrium oxide, and continuing stirring for 20min to obtain the mixed aggregate.

3. The mixed aggregate is 200 parts by weight, the thermoplastic phenolic resin is 9 parts by weight, the coupling agent is 0.45 part by weight (KH550 and KH560 are equal in mass ratio), the urotropin is 0.6 part by weight (a hexamethylenetetramine aqueous solution with the mass fraction of 40 percent), and the lubricating agent is 0.8 part by weight (calcium stearate).

4. Heating the mixed aggregate to 155 ℃, transferring the heated mixed aggregate into a sand mixer, and adding the thermoplastic phenolic resin and the coupling agent into the sand mixer for 72 s; cooling the mixture to 102 ℃, and adding urotropine mixed sand for 35 s; and cooling the mixture to 80 ℃, adding a lubricant for mixing sand for 30s, immediately discharging sand, crushing and screening to obtain the precoated sand.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 134 ℃ and flow-down time 29.3 s.

Example 2

1. Weighing 100 parts of quartz sand, 15 parts of chromium ore sand, 1.4 parts of carbon nano tube and 8.4 parts of nano yttrium oxide according to parts by weight; wherein Cr in the chromium ore sand₂O₃49% of (B), Fe₂O₃The content is 18%, the AFS granularity of quartz sand and chrome sand is 55-65, the nanometer yttrium oxide is not less than 99.99%, the particle size is 30-50nm, the carbon nano tube is pretreated in advance (the carbon nano tube is mixed with acid solution according to the mass volume ratio (g/mL) of 1: 20, the mixture is heated to 100 ℃ for ultrasonic treatment and magnetic stirring, and the mixture is washed, filtered and dried after being condensed and refluxed for 3 hours).

2. Mixing and stirring chrome ore sand and carbon nano tubes for 10min at the rotating speed of 1100r/min, then adding the obtained mixture into quartz sand calcined at 900 ℃ for 2h, mixing and stirring at the rotating speed of 2400r/min for 50min, adding nano yttrium oxide, and continuing stirring for 20min to obtain the mixed aggregate.

3. The mixed aggregate is 200 parts by weight, the thermoplastic phenolic resin is 9 parts by weight, the coupling agent is 0.45 part by weight (KH550 and KH560 are equal in mass ratio), the urotropin is 0.6 part by weight (a hexamethylenetetramine aqueous solution with the mass fraction of 40 percent), and the lubricating agent is 0.8 part by weight (calcium stearate).

4. Heating the mixed aggregate to 155 ℃, transferring the heated mixed aggregate into a sand mixer, and adding the thermoplastic phenolic resin and the coupling agent into the sand mixer for 72 s; cooling the mixture to 102 ℃, and adding urotropine mixed sand for 35 s; and cooling the mixture to 80 ℃, adding a lubricant for mixing sand for 30s, immediately discharging sand, crushing and screening to obtain the precoated sand.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 117 ℃ and flow time 28.8 s.

Example 3

1. Taking 100 parts of quartz sand, 15 parts of chromium ore sand, 3 parts of carbon nano tubes and 6.5 parts of nano yttrium oxide according to parts by weight; wherein Cr in the chromium ore sand₂O₃49% of (B), Fe₂O₃The content is 18%, the AFS granularity of quartz sand and chrome sand is 55-65, the nanometer yttrium oxide is not less than 99.99%, the particle size is 30-50nm, the carbon nano tube is pretreated in advance (the carbon nano tube and acid solution are mixed according to the mass-to-volume ratio (g/mL) of 1: 20)Mixing, heating to 100 ℃, performing ultrasonic treatment and magnetic stirring, performing condensation reflux for 3 hours, washing, filtering and drying).

2. Mixing and stirring chrome ore sand and carbon nano tubes for 10min at the rotating speed of 1100r/min, then adding the obtained mixture into quartz sand calcined at 900 ℃ for 2h, mixing and stirring at the rotating speed of 2400r/min for 50min, adding nano yttrium oxide, and continuing stirring for 20min to obtain the mixed aggregate.

3. The mixed aggregate is 200 parts by weight, the thermoplastic phenolic resin is 9 parts by weight, the coupling agent is 0.45 part by weight (KH550 and KH560 are equal in mass ratio), the urotropin is 0.6 part by weight (a hexamethylenetetramine aqueous solution with the mass fraction of 40 percent), and the lubricating agent is 0.8 part by weight (calcium stearate).

4. Heating the mixed aggregate to 155 ℃, transferring the heated mixed aggregate into a sand mixer, and adding the thermoplastic phenolic resin and the coupling agent into the sand mixer for 72 s; cooling the mixture to 102 ℃, and adding urotropine mixed sand for 35 s; and cooling the mixture to 80 ℃, adding a lubricant for mixing sand for 30s, immediately discharging sand, crushing and screening to obtain the precoated sand.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 137 ℃ and flowing time of 30.4 s.

Example 4

1. Weighing 100 parts of quartz sand, 12 parts of chromium ore sand, 1.8 parts of carbon nano tube and 6.8 parts of nano yttrium oxide according to parts by weight; wherein Cr in the chromium ore sand₂O₃Content of (2%) Fe₂O₃The content is 19%, the AFS granularity of quartz sand and chrome sand is 55-65, the nanometer yttrium oxide is not less than 99.99%, the particle size is 30-50nm, the carbon nano tube is pretreated in advance (the carbon nano tube and an acid solution are mixed according to the mass-to-volume ratio (g/mL) of 1: 20, the mixture is heated to 100 ℃ for ultrasonic treatment and magnetic stirring, and the mixture is washed, filtered and dried after being condensed and refluxed for 3 hours).

2. Mixing and stirring chrome ore sand and carbon nano tubes for 10min at the rotating speed of 1100r/min, then adding the obtained mixture into quartz sand calcined at 900 ℃ for 2h, mixing and stirring at the rotating speed of 2400r/min for 50min, adding nano yttrium oxide, and continuing stirring for 20min to obtain the mixed aggregate.

3. The mixed aggregate is 200 parts by weight, the thermoplastic phenolic resin is 11 parts by weight, the coupling agent is 0.55 part by weight (KH550 and KH560 are equal in mass ratio), the urotropin is 0.6 part by weight (a hexamethylenetetramine aqueous solution with the mass fraction of 40 percent), and the lubricating agent is 0.8 part by weight (calcium stearate).

4. Heating the mixed aggregate to 144 ℃, transferring the heated mixed aggregate into a sand mixer, and adding the thermoplastic phenolic resin and the coupling agent into the sand mixer for 70 seconds; cooling the mixture to 100 ℃, and adding urotropine mixed sand for 32 s; and cooling the mixture to 80 ℃, adding a lubricant for mixing sand for 30s, immediately discharging sand, crushing and screening to obtain the precoated sand.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 122 ℃ and flow-down time 29.7 s.

Comparative example 1

The same procedure as in example 1 was repeated except that the carbon nanotubes were not added during the preparation of the mixed aggregate.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 101 ℃ and flow time 29.5 s.

Comparative example 2

The same as example 1 except that no nano yttrium oxide was added during the preparation of the mixed aggregate.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 130 ℃ and flow time 41.1 s.

Comparative example 3

Aggregate was prepared using only quartz sand and chromium ore sand, and the remaining process parameters were the same as in example 1.

And detecting the melting point and the fluidity of the obtained precoated sand to obtain: melting point 99 deg.C, and flowing time 41.6 s.

The detection standard is as follows: JB/T8583-.

As can be seen from the detection data of the precoated sand obtained in the examples 1 to 4 and the comparative examples 1 to 3, the precoated sand prepared by the method of the present invention has high melting point and good fluidity, while the precoated sand prepared by using the mixed aggregate not doped with the carbon nanotube has poor melting point, and the precoated sand prepared by using the mixed aggregate not doped with the nano yttrium oxide has poor fluidity, which proves that the aggregate prepared by doping the carbon nanotube and the nano yttrium oxide can significantly improve the fluidity of the precoated sand and the melting point thereof.

The above-described embodiments are only preferred embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made by one skilled in the art, and any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.